6-, 1- and 2-Substituted-1-carbadethiapen-2-em-3-carboxylic acids

ABSTRACT

Disclosed are 6-, 1- and 2-substituted-1-carbadethiapen-2-em-3-carboxylic acids having the structure: ##STR1## wherein: R 1 , R 6 , R 7  and R 8  are, inter alia, independently selected from the group consisting of hydrogen, alkyl, alkenyl, aryl and aralkyl. Such compounds as well as their pharmaceutically acceptable salt, ester and amide derivatives are useful as antibiotics. Also disclosed are processes for the preparation of such compounds, pharmaceutical compositions comprising such compounds and methods of treatment comprising administering such compounds and compositions when an antibiotic effect is indicated.

BACKGROUND OF THE INVENTION

This invention relates to 6-, 1- and 2-substituted-1-carbadethiapen-2-em-3-carboxylic acids and derivatives thereof which are useful as antibiotics and which may be represented by the following generic structural formula (I): ##STR2## wherein R¹, R⁶, R⁷ and R⁸ are independently selected from the group consisting of hydrogen, substituted and unsubstituted: alkyl, alkenyl, and alkynyl, having from 1-10 carbon atoms; cycloalkyl, cycloalkylalkyl, and alkylcycloalkyl, having 3-6 carbon atoms in the cycloalkyl ring and 1-6 carbon atoms in the alkyl moieties; aryl, such as phenyl; aralkyl, aralkenyl, and aralkynyl wherein the aryl moiety is phenyl and the linear chain has 1-6 carbon atoms; heteroaryl, heteroaralkyl, heterocyclyl and heterocyclylalkyl; wherein the substituent or substituents relative to the above-named radicals are selected from the group consisting of: amino, mono, di- and trialkylamino, hydroxyl, alkoxyl, mercapto, alkylthio, arylthio such as phenylthio, sulfamoyl, amidino, guanidino, nitro, chloro, bromo, fluoro, cyano and carboxy; and wherein the hetero atom or atoms in the above-named heterocyclic moieties are selected from the group consisting of 1-4 oxygen, nitrogen or sulphur atoms; and wherein the alkyl moieties of the above-recited substituents have 1-6 carbon atoms.

This invention also relates to the carboxyl derivatives of I which are antibiotics and which may be represented by the following generic structure (I): ##STR3## wherein X' is oxygen, sulphur or NR' (R'=H or lower alkyl having 1-6 carbon atoms); and R^(3') is, inter alia, representatively selected from the group consisting of hydrogen, conventional blocking groups such as trialkylsilyl, acyl and the pharmaceutically acceptable salt, ester and amide moieties known in the bicyclic β-lactam antibiotic art; the definition of R^(3') is given in greater detail below.

This invention also relates to processes for the preparation of such compounds (I); pharmaceutical compositions comprising such compounds; and to methods of treatment comprising administering such compounds and compositions when an antibiotic effect is indicated.

There is a continuing need for new antibiotics. For unfortunately, there is no static effectiveness of any given antibiotic because continued wide scale usage selectively gives rise to resistant strains of pathogens. In addition, the known antibiotics suffer from the disadvantage of being effective only against certain types of microorganisms. Accordingly the search for new antibiotics continues.

Thus, it is an objection of the present invention to provide a novel class of antibiotics which are useful in animal and human therapy and in inanimate systems. These antibiotics are active against a broad range of pathogens which representaively include both gram positive bacteria such as S. aureua, Strep. pyogenes, and B. subtilis, and gram negative bacteria such as E. coli, Pseudomonas, Proteus morganii, Serratia, and Klebsiella. Further objects of this invention are to provide chemical processes for the preparation of such antibiotics and their non-toxic pharmaceutically acceptable salts; pharmaceutical compositions comprising such antibiotics; and to provide methods of treatment comprising administering such antibiotics and compositions when an antibiotic effect is indicated.

DETAILED DESCRIPTION OF THE INVENTION

The compounds of the present invention (I, above) are conveniently prepared by the following scheme: ##STR4##

In words relative to the above diagram, the 4-(1,2-substituted-vinyl)azetidine-2-one, 4, starting material is prepared by reacting an R¹ - and R-substituted-oxybutadiene, 1, with chlorosulfonylisocyanate 2. The reaction is conducted without solvent or may be run in solvent such as diethyl ether, ethyl acetate, chloroform, methylene chloride, or the like; at a temperature of from -78° C. to 25° C. for from a few minutes to 1 hour to provide 3. The radical R^(1') is an easily removable acyl blocking group such as an alkanoyl or aralkanoyl which bears no functional group or groups which might interfere with the desired course of reaction (1+2→3→4). Intermediate species 3 is converted to the sulfinamide by reduction which is then hydrolyzed to 4 at pH 6-8. Typically the reaction solution comprising 3 is contacted (5-30 minutes) with an aquoeus solution (at 0°-25° C.) of a reducing agent such as sodium sulfite, thiophenol, or the like at pH 6-8 to provide 4.

The reaction 4→5 is a reduction, and is preferably achieved by hydrogenation in a solvent such as ethyl acetate, ether, dioxane, tetrahydrofuran (THF), ethanol, or the like at 0° to 25° C. for from 5 minutes to 2 hours under 1 to 10 atmospheres of hydrogen in the presence of a hydrogenation catalyst such as a platinum metal or oxide thereof such as 10% Pd/C or the like.

The de-blocking reaction 5→6 is usually desirable when R^(1') is acyl to permit the later alkylation, 7→8. The preferred de-blocking procedure is by alcoholysis wherein the solvent is a lower alkanol such as methanol, ethanol, or the like in the presence of the corresponding alkali metal alkoxide, such as sodium methoxide. Typically, the reaction is conducted for from 5 minutes to 1 hour at a temperature of from -10° to 25° C.

Blocking groups R³ and R² are established (6→7) to provide a suitably protected species for alkylation (7→8→9). There is no criticality in the choice of blocking groups, provided only that they do not interfere with the intended alkylation. R³ may be hydrogen, a triorganosilyl group such as trimethylsilyl, t-butyldimethylsilyl or the like; or a cyclic ether such as 2-tetrahydropyranyl; R² may also be a cyclic ether such as 2-tetrahydropyranyl; alternatively, R³ and R² may be joined together to form protected species such as 7a: ##STR5## For example, species such as 7a are conveniently prepared by treating 6 with 2,2-dimethoxypropane in the presence of a catalyst such as boron trifluoride etherate, toluene sulphonic acid, or the like in a solvent such as methylene chloride, ether, chloroform, dioxane or the like at a temperature of from -10° C. to 35° C. for from a few minutes to 1 hour. Species 7 can be mono- or dialkylated at ring position 6. Alkylation of 7 provides 8. Typically, 7 is treated with a strong base such as lithium diisopropylamide, sodium hydride, phenyl lithium or butyl lithium and the like in a solvent such as tetrahydrofuran (THF), ether, dimethoxyethane and the like at a temperature of from -80° C. to 0° C., whereupon the alkylation agent of choice, R⁶ X, is added (R⁶ is as described above and X is chloro, iodo or bromo; altneratively the alkylating agent may be R⁶ -tosylate, R⁶ -mesylate or an aldehyde or ketone such as acetaldehyde and the like) to provide monoalkylated species 8. When desired dialkylated species 9 may be obtained from 8 by repeating the alkylating procedure 7→8.

The de-blocking reaction 9→10 is typically conducted by acid hydrolysis such as aqueous acetic acid at a temperature of from 25° C. to 75° C. for from 5 minutes to 3 hours.

The aldehyde intermediate 11 is prepared by treating 10 with an oxidizing agent such as CrO₃.2(pyridine) in CH₃ CN, 1:1 mixture of dimethylsulfoxide and acetic anhydride, cyclohexylcarbodiimide in DMSO, pyridium chlorochromate in CH₂ Cl₂, or the like at a temperature of from 0°-25° C. for from 5 minutes to 1 hour. The resulting species 11 in a solvent such as acetonitrile, methylene chloride, chloroform or the like at a temperature of from -10° to 25° C. is treated with an excess of the reagent HSR⁸ in the presence of an acid catalyst such as boron trifluoride etherate, toluene sulphonic acid or the like to provide 12. Typically, the reaction requires from 1 to 60 minutes.

The vinyl sulphide 14 is obtained via intermediate 13 by treating 12 with a halogen such as chlorine or bromine (X═Cl or Br) in a solvent such as ethyl, methylene chloride, tetrahydrofuran, glyme or the like at a temperature of from -78° to 30° C. for from 1 to 30 minutes followed immediately by treating with an olefin such as cyclohexene, isobutylene, or the like in the presence of base such as triethylamine, DBU, sodium hydride, or the like in a solvent such as DMF, glyme, THF, HMPA. The solution is held at -20° to 25° C. for from 1 to 8 hours to yield 14.

The vinyl sulphide species 14 is reacted with a diester of oxomalonic acid (or its monohydrate) to provide 15. There is no criticality as to the identity of the ester moiety, R⁵, of the oxomalonic acid. R⁵ may be a conventional, easily removable blocking group or it may be a pharmaceutically acceptable ester moiety. Suitable ester radicals R⁵ are p-nitrobenzyl, benzyl, o-nitrobenzyl, t-butyl, 2,2,2-trichloroethyl. The reaction 14→15 is typically conducted in a high boiling organic solvent such as benzene, toluene, cyclohexane, halo aromatic or the like at a temperature of from about 50° C. to reflux for from 0.5 to 6 hours.

The halogenation reaction 15→16 is typically conducted in a solvent such as THF, glyme, ether, methylene chloride, chloroform or the like in the presence of a halogenating agent such as thionyl chloride, phosphorous pentachloride or the like in the presence of base such as pyridine at a temperature of from -20° to 25° C. for from 5 minutes to 3 hours. The selective reduction of 15→17 via 16 is completed by treating 16 with tributylphosphine, triphenylphosphine, or the like in aqueous DMF or similar aqueous systems involving dioxane, THF, glyme, DMSO, or acetone at a temperature of from about 0°-50° C. for from 10 minutes to 5 hours.

Species 17 is halogenated by the previous procedure (12→13), but omitting the addition of the cyclohexene or other olefin, to provide the dihalo species 18. Species 18 is treated with a base such as triethylamine, sodium hydride or potassium hydride in a solvent such as DMF, acetonitrile, methylene chloride, chloroform, glyme or the like at a temperature of from about -78° to 25° C. for 1 to 5 hours to provide 19. Species 19 is converted to 20 on treatment with a strong base such as 1,5-diazabicyclo[5.4.0]undec-5-ene(DBU), 1,5-diazabicyclo[3.4.0]non-5-ene (DBN), or the like in a solvent such as DMSO, acetone, chloroform, DMF, THF, glyme or the like or on treatment with AgF in pyridine at a temperature of from 0°-40° C. for from 1/4 to 24 hours. The reaction 20→21 is conducted by treating 20 with an aromatic base such as pyridine, aqueous dimethylsulfoxide, s-collidine or lutidine, in the presence of a displacing agent such as lithium iodide, sodium chloride, lithium bromide, sodium bromide, or the like at a temperature of from about 80°-150° C. for from 15 minutes to 2 hours. An aqueous work up of the resulting reaction mixture provides 21. Isomerization of the double bond 21→22 is accomplished by treating 21 in a solvent such as DMF, DMSO, ethyl, ether, THF, glyme, methylene chloride with a strong base such as diisoprypylamine, DBU, DBN, or the like at a temperature of from 0° to about 25° C. for from a few minutes to 2 hours or until equilibrium has been established as determined by examination of sample aliquots by ultraviolet absorption or by thin layer chromatography. The final reaction 22→I (hydrogenolysis of the blocking group) is accomplished by treating 22 in a solvent such as dioxane, ethanol, THF or the like or an aqueous mixture thereof in the presence of a platinum metal catalyst such as Pd/C under a hydrogen pressure of from 1-4 atmospheres for from 0.5 to 8 hours at a temperature of from about 0°-25° C.

In the foregoing description of the invention, suitable reagents HSR⁸ (11→12) are representatively illustrated by the following list:

HSCH₂ CH₂ CH₂ NHCO₂ PNB,

PNBO₂ CNHCH₂ CH₂ CH₂ SX, ##STR6## HSC(CH₃)₂ CH₂ NHCO₂ PNB, HSφ,

HSCH₂ φ,

HSC(CH₃)₃,

HSCφ₃, ##STR7## and the like (φ=phenyl; and PBN=p-nitrobenzyl), CH₃ SH,

CH₃ CH₂ SH,

CH₃ (CH₂)₂ SH,

(CH₃)₂ CHSH,

CH₃ (CH₂)₃ SH,

(CH₃)₂ CH(CH₂)₂ SH,

CH₂ .tbd.CHCH₂ SH,

CH.tbd.CCH₂ SH, ##STR8## φ(CH₂)₃ SH(φ=phenyl), φ(CH₂)₂ SH,

HO(CH₂)₂ SH,

H₂ N(CH₂)₂ SH,

H₂ N(CH₂)₃ SH,

CH₃ (CH₂)₂ NH(CH₂)₂ SH, ##STR9## (CH₃)₂ N(CH₂)₂ SH, (CH₃ CH₂)₂ N(CH₂)₂ SH,

HO₂ C(CH₂)₂ SH,

φCH₂ SH, ##STR10##

Similarly, suitable alkylating agents for establishing R⁶ and/or R⁷ ar ring position 6 (7→8→9) are:

φCH₂ CHO,

φCH₂ CH₂ CHO,

CH₂ O,

CH₃ I,

φCH Br,

CH₃ COCH₃.

Relative to the compounds of the present invention I: ##STR11## the most preferred values for R¹ include: ethyl,

propyl,

isopropyl,

cyclopropyl,

phenyl

benzyl.

The most preferred radicals for R⁶ and R⁷ are: R⁶ =H and R⁷ is selected from hydroxymethyl, 1-hydroxyethyl, 1-hydroxypropyl, 2-hydroxypropyl, 2-hydroxyethyl, the most preferred values for R⁸ are: aminoethylthio, aminopropylthio, aminocyclopropylthio, aminoisopropylthio, amidinoisopropylthio.

Especially preferred embodiments of the present invention are those wherein R¹ is selected from the group consisting of methyl, ethyl, propyl, isopropyl, cyclopropyl, phenyl, benzyl, and 2-bromoethyl.

The compounds made available by the present invention are valuable antibiotics active against various gram-positive and gram-negative bacteria and, accordingly, find utility in human and veterinary medicine. Such sensitive bacteria representatively include: Staphylococcus aureua, Escherichia coli, Klebsiella pneumoniae, Serratia, Salmonella typhosa, Pseudomonas and Bacterium proteus. The resulting compounds may further be utilized as additives to animal feed, for preserving foodstuffs, and as disinfectants. For example, they may be employed in aqueous compositions in concentrations ranging from 0.1 to 100 parts of antibiotic per million parts of solution in order to destroy and inhibit the growth of harmful bacteria on medical and dental equipment and as bactericides in industrial applications, for example, in waterbased paints and in the white water of paper mills to inhibit the growth of harmful bacteria.

These antibiotics may be used alone or in combination as an active ingredient in any one of a variety of pharmaceutical preparations. These antibiotics and their corresponding salts may be employed in capsule form or as tablets, powders or liquid solutions or as suspensions or elixirs. They may be administered orally, intravenously or intramuscularly.

Tablets and capsules for oral administration may be in unit dose presentation form, and may contain conventional excipients such as binding agents, for example, syrup, acacia, gelatin, sorbitol, tragacanth, or polyvinylpyrrolidone; fillers for example, lactose, sugar, maize-starch, calcium phosphate, sorbitol or glycine; lubricants, for example, magnesium stearate, talc, polyethylene glycol, silica; disintegrants, for example, potato starch or acceptable wetting agents such as sodium lauryl sulphate. The tablets may be coated according to methods well known in the art. Oral liquid preparations may be in the form of aqueous or oily suspension, solution, emulsions, or syrups; or may be presented as a dry product, for reconstitution with water or other suitable vehicles before use. Such liquid preparations may contain conventional additives such as suspending agents, for example, sorbitol, syrup, methyl cellulose, glucose/sugar syrup, gelatin, hydroxyethylcellulose, carboxymethyl cellulose, aluminum stearate gel or hydrogenated edible oils, for example almond oil, fractionated coconut oil, oily esters, propylene glycol, or ethyl alcohol; preservatives, for example methyl or propyl p-hydroxybenzoates or sorbic acid.

Compositions for injection may be presented in unit dose form in ampules, or in multidose container. The compositions may take such forms as suspensions, solutions, or emulsions in oily or aqueous vehicles, any may contain formulatory agents such as suspending, stabilizing and/or dispersing agents. Alternatively, the active ingredient may be in powder form for reconstitution with a suitable vehicle, e.g., sterile, pyrogen-free water, before use.

The compositions may also be prepared in suitable forms for absorption through the mucous membranes of the nose and throat or bronchial tissues and may conveniently take the form of powder or liquid sprays or inhalants, lozenges, throat paints, etc. For medication of the eyes or ears, the preparations may be presented as individual capsules, in liquid or simi-solid form, or may be used as drops etc. Topical applications may be formulated in hydrophobic or hydrophilic bases as ointments, creams, or lotions.

Also, in addition to a carrier, the instant compositions may include other ingredients such as stabilizers, binders, antioxidants, preservatives, lubricators, suspending agents, viscosity agents or flavoring agents and the like. In addition, there may also be included in the compositions other active ingredients to provide a broader spectrum of antibiotic activity.

For veterinary medicine the composition may, for example, be formulated as an intramammary preparation in either long or quick-release bases.

The dosage to be administered depends to a large extent upon the general health and weight of the subject being treated, and the route and frequency of administration--the parenteral route being preferred for generalized infections and the oral route for intestinal infections. In general, a daily oral dosage consists of from about 2 to about 600 mg. of active ingredient per kg. of body weight of the subject in one or more applications per day. A preferred daily dosage for adult humans lies in the range of from about 15 to 150 mg. of active ingredient per kg. of body weight.

The instant compositions may be administered in several unit dosage forms as, for example, in solid or liquid orally ingestible dosage form. The compositions per unit dosage, whether liquid or solid may contain from 0.1% to 99% of active material, the preferred range being from about 10-60%. The composition will generally contain from about 15 mg. to about 1500 mg. of the active ingredient; however, in general, it is preferably to employ a dosage amount in the range of from about 100 mg. to 1000 mg. In parenteral administration the unit dosage is usually the pure compound in a slightly acidified sterile water solution or in the form of a soluble powder intended for solution.

Especially preferred pharmaceutically acceptable salts and esters involving the carboxyl group of compounds of the present invention (I) are disclosed and claimed in co-pending U.S. Patent Application Ser. No. 861,314 (filed Dec. 16, 1977), which application is directed, inter alia, to pharmaceutically acceptable salts and esters of the carboxyl group of thienamycin. It is precisely these salts and esters which are preferred in the present invention and they are prepared in a manner analogous to that disclosed in U.S. Patent Application Ser. No. 861,314, which is incorporated herein by reference. Thus, especially preferred salts include sodium, potassium, ammonium, and the like; and especially preferred esters include pivaloxymethyl, p-t-butylbenzyl, 5-indanyl, 3-phthalidyl, 3-methyl-2-butenyl, and the like. One should note that when, in the total synthesis outlined above, R² is a pharmaceutically acceptable ester moiety, there is no need for the final deblocking step if it is desired to have the final product I in the form of a pharmaceutically acceptable ester.

Especially preferred embodiments of the present invention are those, as defined above, except that any unsubstituted amino group borne on radical R⁸ of Structure I is derivatized according to the teachings of Belgium Pat. No. 848,545 (issued May 20, 1977); the resulting amino group being represented thusly (partial structure): ##STR12## wherein X and Y are defined by the publication; species wherein X is H or lower alkyl and Y is NH₂ are especially preferred.

The following examples, illustrate but do not limit the product, process, compositional or method of treatment aspects of the present invention. All reaction temperatures are in °C.

EXAMPLE 1 ##STR13##

The α,β-unsaturated aldehydes (C) are prepared by modified procedures reported by M. B. Green and W. J. Hickinbottom in J. Chem. Soc. 3262 (1957); and W. J. Bailey and R. Barclay Jr., J. Org. Chem., 21, 328 (1956).

Acetaldehyde (1 eq.) and propionaldehyde (R^(3=CH) ₃) (1 eq.) are placed in a three-necked round-bottom flask which is equipped with a mechanical stirrer, a dry-ice condenser, and a pressure equalized dropping-funnel. To the solution is added dropwise 1 eq. of 1 N NaOH through the dropping funnel with constant stirring. After completion of the mixing, the mixture is stirred for 10 min, then poured into a beaker containing crushed ice. Extraction of the mixture with ether gives crude product. The desired product (C) is obtained by fractional distillation through a Widmer column.

Isopropenyl acetate (2 eq), cupric acetate (0.002 eq) p-toluenesulfonic acid (0.008 eq) and the α,β-unsaturated aldehyde C(1 eq.) are placed in a three-necked round-bottom flask equipped with a thermometer, a nitrogen inlet tube and a Widmer column which is attached with a distillation head. The mixture is heated at 93°-110° C. until quantitative acetone is collected. The mixture is then allowed to cool to r.t. and filtered from solids. The dark brown filtrate is mixed with triethanolamine in water at 0° C. The two layer mixture is distilled quickly under reduced pressure. The organic layer of the distillate is separated. The aqueous layer is extracted with 200 ml ether. The combined organic layer is washed with 10% K₂ CO₃, dried over Na₂ SO₄, and evaporated in vacuo. The residue so obtained is mixed with 2.0 g N-phenyl-β-naphthamine and distilled under reduced pressure to give the desired 2-substituted 1-acetoxy-1,3-butadiene (1').

Following the procedure of Example 1, the following R³ substituted species are obtained. (Table I).

                  TABLE I                                                          ______________________________________                                          ##STR14##                                                                            R.sup.3    R                                                            ______________________________________                                         1.       CH.sub.3                                                                                     ##STR15##                                               2.       CH.sub.3 CH.sub.2                                                                            ##STR16##                                               3.       CH.sub.3 CH.sub.2 CH.sub.2                                                                   ##STR17##                                                         ##STR18##                                                                                   ##STR19##                                                         ##STR20##                                                                                   ##STR21##                                               6.       Ph (Ph = phenyl)                                                                             ##STR22##                                               7.       PhCH.sub.2                                                                                   ##STR23##                                               ______________________________________                                    

EXAMPLE 2 Preparation of 6-(1-hydroxyethyl)-1-methyl-2-(2-amino-1-methylethylthio)carbadethiapen-2-em-3-carboxylic acid ##STR24## Step A Preparation of 1' ##STR25##

Isopropenyl acetate (182 g), cupric acetate (0.40 g), 2-methyl-2-butenal (84 g) and p-toluenesulfonic acid (1.52 g) are placed in a 1.0-1, three-necked flask equipped with a thermometer, a nitrogen inlet tube and a 10-in. Widmer column which is attached with a distillation head. The mixture is heated at 93°-110° C. until 73 ml of acetone is collected. After cooling to r.t. (25° C.) the mixture is filtered from solids. The dark brown filtrate is cooled in an ice-bath and mixed with 3.4 g triethanolamine in 200 ml water. The two layer mixture is distilled quickly at 53 mm (b.p. 54° C.). The organic layer of the distillate is separated. The aqueous layer is extracted with 200 ml ether. The organic layers are combined and washed with 10% K₂ CO₃, dried over Na₂ SO₄, and evaporated in vacuo. The residue so obtained is mixed with 2.0 g N-phenyl-β-naphthamine and distilled under reduced pressure to give 1'(97 g), b.p. 81°-91° (66 mm).

Step B Preparation of 2' and 3' ##STR26##

Chlorosulfonylisocyanate (CSI) (6.5 ml) is placed in a three-necked, 100-ml flask equipped with a thermometer, a magnetic stirring bar, a nitrogen inlet tube and a 25-ml pressure-equalized dropping funnel. The CSI is chilled to -50° C. and mixed with 12.5 ml ether through the dropping funnel. The etheral solution of CSI is allowed to warm up to -25° C.; to the solution is added dropwise 1-acetoxyl-2-methyl-1,3-butadiene (1') (5.9 ml in 12.5 ml ether) in 30 min. The mixture is then stirred for 20 min at -20°±3° C. The white precipitate formed initially is redissolved at the end of the reaction.

In a 500-ml round bottom flask, a solution of 10 g sodium sulfite and 25 g potassium hydrogen phosphate in 100 ml water is prepared and is cooled in an ice bath. Ether (100 ml) and crushed ice (100 g) are added and the mixture is vigorously stirred in an ice bath. At the end of 20 minutes reaction time, the reaction mixture which contains 2' is transferred into the dropping funnel and added dropwise to the hydrolysis mixture in 5 minutes. The hydrolysis is allowed to continue for an additional 30 minutes at 3° C. The organic layer is separated and the aqueous is extracted with 50 ml ether. The organic layers are combined, dried over Na₂ SO₄ and evaporated to give crystalliine product 3' (2.3 g), m.p. 77°-78,5°; m.s. (169(M⁺); IR 1760 cm⁻¹ (β-lactam); NMR (300 MHz, CDCl₃): 1.70 (d), 2.16(s), 2.84 (qq), 3.18 (qq), 4.20 (m), 5.82 (broad, and 6.26 (s) ppm.

Step C Preparation of 4' ##STR27##

4-(1-methyl-2-acetoxyvinyl)azetidine-2-one (3') (6.5 g) is hydrogenated on a Parr shaker at r.t. under 40 psi hydrogen in the presence of 10% Pc/C (0.6 g) in 200 ml ethylacetate for 2 hr. The mixture is filtered from the catalyst and the filtrate is evaporated in vacuo to give the crude product. Purification of the crude product by high pressure liquid chromatograph (HPLC) (silical gel column, 30% ethylacetate/CH₂ Cl₂ solvent system) affords a white crystalline product 4' (6.04 g) after evaporation of solvent. The product shows following physical characteristics: ms 171 (M⁺); IR(Neat) 1754 cm⁻¹ ; NMR (60 MHz, CDCl₃): 0.96 (d), 1.01 (d), 2.06 (d, OAc), 2.75-3.80 (m), 3.99 (d) and 6.80 (broad) ppm.

STEP D Preparation of 5' ##STR28##

Under N₂ at 0°, a solution of 4-(1-methyl-2-acetoxyethyl)-2-azetidinone 4' (1.2 g) in 10 ml methanol is treated with sodium methoxide (57 mg). After stirring for 1 hr, the solution is neutralized with glacial acetic acid (65 mg). Removal of methanol in vacuo gives crude 4-(1-methyl-2-hydroxyethyl)-2-azetidinone (5') as an oil. The product is purified chromatography on silica gel eluting with ethyl acetate and to give 0.78 g of 5':

IR (neat): 1740 cm⁻¹ ;

NMR (CDCl₃): 0.77 (d), 0.96 (d), 1.90 (m), 2.60-3.30 (m), 3.60 (m), 4.19 (s), and 7.23 (s). The product crystallizes as colorless solids in the refrigerator.

STEP E Preparation of 6' ##STR29##

A solution of 4-(1-methyl-2-hydroxyethyl)-2-azetidinone (0.5 g) and 2,2-dimethoxypropane (0.48 g) in 10 ml anhydrous methylene chloride is treated with boron trifluoride (55 mg) at room temperature for 90 min. The mixture is washed with 5 ml saturated NaHCO₃. The organic layer is separated, dried over Na₂ SO₄ and allowed to evaporate in vacuo to give crude isomeric mixture of 6' (0.48 g) as an oil.

Separation of isomers 6'α and 6'β is accomplished by high pressure liquid chromatograph (HPLC) (silica gel) eluting with 40% ethylacetate/hexanes. After evaporation of the solvents affords 150 mg of 6'β as an oil and 200 mg of 6'α as a white solid.

NMR (300 MHz, CDCl₃) of 6'α: 0.81 (d), 1.31 (s), 1.68 (s), 1.62 (m), 2.52 (q), 3.05 (m), 3.42 (t), and 3.66 ppm (q), NMR (300 MHz, CDCl₃) of 6'β: 1.10(d), 1.38 (s), 1.67 (s), 1.90 (m), 2.80 (q), 2.86 (q), 3.62 (q), 3.78 (m) and 3.98 (q) ppm.

STEP Fa Preparation of 7'α ##STR30##

At -78° C., diisopropylamine (2.2 g) in 20 ml of anhydrous tetrahydrofuran is treated with n-butyllithium (1.6 M in n-hexane, 14 ml) for 5 min. To the solution is added 8-oxo-5α, 2,2-trimethyl-1-azabicyclo[4.2.0]octane (6'α) (3.4 g) and the mixture is stirred for 10 min. The resulting lithium enolate is treated with acetaldehyde (1.68 ml). The mixture is stirred for 1 min. then is quenched with 24 ml saturated ammonium chloride at -78° C., then allowed to warm to room temperature (25° C.). The mixture is extracted with ethylacetate (2×100 ml). The organic layer is separated, dried over Na₂ SO₄ and allowed to evaporate in vacuo to give 4.5 g of the crude product 7'α.

The crude isomeric mixture of 7'α is purified and separated by HPLC (silica gel) eluting with 50% ethylacetate/methylene chloride to give 3.5 g of trans-7'α and 0.5 g of cis-7'α. Both isomers are crystalline solids.

STEP Fb Preparation of 7'β ##STR31##

Following the procedure of Step Fa, except replacing the starting material 6'α with 6'β isomer, the products, trans-7'β (4.0 g) and cis-7'β (0.1 g), are obtained.

STEP Fc Preparation of 7"β ##STR32##

Under anhydrous conditions at 0° C. a solution of R enriched trans-7'β (2.90 g) in 60 ml methylene chloride is treated 4-dimethylaminopyridine (3.32 g) and p-nitrobenzylchloroformate (5.88 g). The mixture is allowed to warm to room temperature and stirred for 1 hr. The resulting mixture is washed with 0.1 N Hcl, water, brine and water. The organic layer is separated, dried over Na₂ SO₄ and allowed to evaporate in vacuo to give crude products. The crude products dissolved in 20 ml ether and chilled at -5° C. give the o-nitrobenzyl alcohol (0.5 g) which is separated by filtration. The isomeric mixture trans-7"β is purified and separated by HPLC (silica gel) eluting with 40% ethylacetate/cyclohexane to give 1.2 g of S-trans-7"β and 1.0 g of R-trans-7"β.

The spectra data of T-trans-7"β:

NMR (300 MHz, CDCl₃): 1.12 (d), 1.40 (s), 1.46 (d), 1.73 (s), 1.95 (m), 3.20 (q), 3.60 (q), 3.74 (q), 3.95 (q), 5.07 (m), 5.58 (q), 7.56 (t), 7.70 (m) and 8.19 (d)ppm.

The spectra data of S-trans-7"β:

NMR (300 MHZ, CDCl₃): 1.10 (d), 1.40 (s), 1.43 (d), 1.72 (s), 1.94 (m), 3.34 (q), 3.61 (q), 3.67 (q), 3.96 (q), 5.13 (m), 5.64 (d), 7.53 (m), 7.68 (m), and 8.17 (d)ppm.

STEP Fd Preparation of 7"α ##STR33##

Following the procedure of Step Fc; except replacing the starting material trans-7'β with trans-7'α isomer, the products R-trans-7"α and S-trans-7"α are obtained.

    TABLE II       ##STR34##       ##STR35##       ##STR36##       ##STR37##       ##STR38##       ##STR39##       ##STR40##      (ONB = onitrobenzyl)

STEP Ga Preparation of R-trans-9'β: ##STR41##

8-Oxo-3-oxa-5β-2,2-trimethyl-7α-(1R-o-nitrobenzyl)carbonyldioxyethyl)-1-azabicyclo[4.2.0]octane (R-trans-7"β) (2.1 g) is dissolved in 4 ml trifluoroacetic acid and 4 ml water at room temperature and the mixture is stirred for 10 minutes. The resulting homogeneous solution is slowly poured into a vigorously stirred saturated solution of potassium bicarbonate (30 ml) in a 200-ml beaker. The mixture is extracted with methylene chloride (200 ml). The organic layer is separated, dried over Na₂ SO₄ and allowed to evaporate in vacuo to give crude product 9' which is purified by a silica gel column eluting with 40% ethylacetate/cycylhexane to afford product R-trans-9'β as an oil.

NMR (300 MHz, CDCl₃): 0.98 (d), 1.28 (d), 2.85 (m), 3.20 (q), 3.62 (m), 5.12 (m), 5.57 (q), 6.40 (s), 7.53 (t), 7.66 (m) and 8.14 (d).

Step Gb

Following the procedure of Step Gb, except systematically replacing the starting material with the other isomers, the other isomeric products are obtained (Table III). Equivalently R may be the para- isomer.

                  TABLE III                                                        ______________________________________                                          ##STR42##                                                                     Starting material Product                                                      ______________________________________                                          ##STR43##                                                                                        ##STR44##                                                    ##STR45##                                                                                        ##STR46##                                                    ##STR47##                                                                                        ##STR48##                                                    ##STR49##                                                                                        ##STR50##                                                    ##STR51##                                                                                        ##STR52##                                                    ##STR53##                                                                                        ##STR54##                                                    ##STR55##                                                                                        ##STR56##                                                     STEPS H-K Steps H, I, J and K complement Steps E, Fa-d, and G for the        preparation of 3-(1-p(and o)-nitrobenzylcarbonyldioxyethyl)-4-(1-methyl-2-     hydroxyethyl)azetidinone                                                        ##STR57##                                                                       STEP H Preparation of 1-(2-Tetrahydropyranyl)-4-[1-methyl-2-(2-tetrahydr     opyranyl)oxyethyl]-2-azetidinone                                                ##STR58##                                                                     Under nitrogen and at 25° C., a solution of 4-(1-methyl-2-hydroxyet     hyl)-2-azetidinone (62 mg), in 0.5 ml of anhydrous p-dioxane is treated        with 2,3-dihydropyran (0.98 ml) and p-toluenesulfonic acid monohydrate         (19 mg). The resulting solution is stirred for a period of 60 minutes and      then partitioned between 10 ml of 0.5 M pH 7 phosphate buffer and 10 ml        of ethyl acetate. The aqueous phase is extracted a second time with ethyl      acetate. The combined ethyl acetate solutions are washed with brine,           dried over magnesium sulfate and filtered. The filtrate is evaporated          under reduced pressure to give 216 mg of crude product. Purification by        preparative thick-layer chromatography developing with ethyl acetafte,         gives 80 mg of 1-(2-tetrahydropyranyl)-4-[1-methyl-2-(2-tetrahydropyranyl)     -oxyethyl]-2-azetidinone as an oil. STEP I Preparation of Cis and              Trans-1-(2-tetrahydropyranyl)-3-(1-hydroxyethyl)-4-[1-methyl-2-(2-tetrahyd     ropyranyl)-oxyethyl]-2-azetidinone                                              ##STR59##                                                                     Following the procedure described for the preparation of      8-oxo-2,2,5-trimethyl-7α and      β-(1-hydroxyethyl)-3-oxa-1-azabicyclo[4.2.0]octane from      8-oxo-2,2,5-trimethyl-3-oxa-1-azabicyclo[4.2.0]octane and using      1-(2-tetrahydropyranyl)-4-[1-methyl-2-(2-tetrahydropyranyl)oxyethyl]-2-aze     tidinone one obtains a diastereomeric mixture of both cis and      trans-1-(2-tetrahydropyranyl)-3-(1-hydroxyethyl)-4-[1-methyl-2-(2-tetrahyd     ropyranyl)oxyethyl]-2-azetidinone.

STEP J Preparation of Cis and Trans-1-(2-tetrahydropyranyl)-3-(1-p-nitrobenzylcarbonyldioxyethyl)-4-[1-methyl-2-(2-tetrahydropyranyl)oxyethyl]-2-azetidinone ##STR60## Following the procedure described for the preparation of 8-oxo-2,2,5-trimethyl-7α-(1-p-nitrobenzylcarbonyldioxyethyl)-3-oxa-1-azabicyclo[4.2.0]octane from 8-oxo-2,2,5-trimethyl-7α-(1-hydroxyethyl)-3-oxa-1-azabicyclo[4.2.0]octane and using trans-1-(2-tetrahydropyranyl)-3-(1-hydroxyethyl)-4-[1-methyl-2-(2-tetrahydropyranyl)oxyethyl]-2-azetidinone there is obtained trans-1-(2-tetrahydropyranyl)-3-(1-p-nitrobenzylcarbonyldioxyethyl)-4-[1-methyl-2-(2-tetrahydropyranyl)oxyethyl]-2-azetidinone. The cis diastereoisomers are obtained in an analogous manner. STEP K Preparation of Cis and Trans-3-(1-p-nitrobenzylcarbonyldioxyethyl)-4-(1-methyl-2-hydroxyethyl)-2-azetidinone ##STR61## A solution of trans-1-(2-tetrahydropyranyl)-3-(1-p-nitrobenzylcarbonyldioxyethyl)-4-[1-methyl-2-(2-tetrahydropyranyl)oxyethyl]-2-azetidinone in methanol at 25° C. is treated with 0.1 molar equivalent of p-toluenesulfonic acid monohydrate. The solution is stirred for a period of 2 hours and then neutralized with 1 M pH 7 phosphate buffer. The product is extracted into ethyl acetate. The ethyl acetate solution is washed with brine, dried over magnesium sulfate and filtered. The filtrate is evaporated under reduced pressure to give trans-3-(1-p-nitrobenzylcarbonyldioxyethyl)-4-(1-methyl-2-hydroxyethyl)-2-azetidinone. The cis diastereoisomers are obtained in an analogous manner. STEP L Preparation of 12 ##STR62## To 6.75 ml anhydrous pyridine (83.9 mmole) in 350 ml anhydrous acetonitrile is added 4.05 g anhydrous powedered chromium trioxide (mw=100; 40.5 mmole). After stirring at room temperature (25° C.) for 30 minutes, 9.6 g dried Supercell is added and stirring is continued for 5 additional minutes. A solution of 3.21 g trans-3-(1-p-nitrobenzylcarbonyldioxyethyl)-4-(1-methyl-2-hydroxyethyl)-2-azetidinone in 30 ml anhydrous acetonitrile is added all at once. The reaction mixture is stirred under anhydrous conditions at room temperature (25° C.) for one hour. Additional of 9.6 g NaHSO₃ is followed by 5 minutes of stirring after which the reaction mixture is filtered through a mixed packed bed of 40 g silica gel and 40 g anhydrous magnesium sulfate. The bed is washed repeatedly with acetonitrile (total volume of filtrate 600 ml). The filtrate is concentrated under a N₂ stream to 130 ml total volume. To this solution containing crude aldehyde at 0° C. under N₂ is added 9.64 g 1-(p-nitrobenzyloxycarbonylamino)-2-propanethiol as prepared below (Step M). To the stirred reaction mixture is mixture is added 8.0 ml boron trifluoride etherate (63.4 mmole). After 1.5 hours at 0° C. the reaction mixture is poured into a stirred ice-cold mixture of 69 g K₂ HPO₄ -500 ml H₂ O and 700 ml ethyl acetate (EA). The layers are separated, and the aqueous one is saturated with NaCl and re-extracted with additional EA. The combined organic layers are washed twice with brine, dried over anhydrous MgSO₄ and filtered. The filtrate is concentrated under a N₂ stream and then pumped on high vacuum to give crude 12.

The material is chromatographed on 450 g silica gel (column height=48 cm; diameter=5.5 cm) packed and applied in CHCl₃ and eluted with increasing percentages of MeOH in CHCl₃ (0-4% MeOH/CHCl₃). Those fractions containing the desired product are combined, concentrated under a N₂ stream; and pumped on high vacuum to give 12.

STEP M Preparation of 1-(p-Nitrobenzyloxycarbonylamino)-2-propanethiol ##STR63## To 600 ml diethyl ether (Et₂ O)-75 ml H₂ O in an ice bath with stirring is added 3.2 g 1-amino-2-propanethiol hydrochloride (28.1 mmole). A solution of 7.14 g NaHCO₃ (85 mmole) in 75 ml H₂ O is added. The ice bath is removed, and at room temperature a solution of 6.75 g p-nitrobenzylchloroformate (31.3 mmole) in 270 ml Et₂ O is added dropwise over a period of one hour. After 10 additional minutes. the layers are separated. The ether layer is extracted with 150 ml 0.25 HCl, and then with 200 ml brine. Each aqueous layer is then backwashed successively with 100 ml Et₂ O. The combined ET₂ O layers are dried over anhydrous MgSO₄, filtered, and concentrated under a N₂ stream. The crystalline residue is slurried in a small amount of ether, filtered, and the pale yellow crystals are dried under high vacuum to give 4.7 g product. STEP N Preparation of 14 ##STR64##

To 14.2 ml pentane (dried over 4 A Linde molecular sieves) is added 0.5 ml Br₂. To 5 g of 12 in 58 ml tetrahydrofuran (THF) (freshly distilled from lithium aluminum hydride (LAH) and 65 ml Et₂ O (dried over 3 A 1/16" Linde molecular sieves) at 0° C. under N₂ with stirring is added dropwise 10 ml of the above 0.66 M Br₂ solution. After 10 minutes at 0° C., 0.67 ml cyclohexene is added. After 5 minutes at 0° C., 1.7 ml triethylamine is added immediately followed by 40 ml ice-cold dimethylformamide (DMF) (distilled from anhydrous CaSO₄ at 40 mm and stored over 4 A Linde molecular sieves). The ice bath is removed, and stirring is continued for 21/4 hours at room temperature. The reaction mixture is poured into a stirred ice-cold mixture of 12.6 ml 1 M KH₂ PO₄ 160 ml H₂ O-500 ml (EA). After separation of the layers, the aqueous one is saturated with sodium chloride and re-extracted with EA. The combined organic layers are extracted once with brine, dried over anhydrous MgSO₄, filtered and concentrated under a N₂ stream followed by pumping under high vacuum to provide crude 14.

The material is chromatographed on 250 g silica gel (height=45 cm; diameter=4.5 cm) packed and applied in CHCl₃ and eluted with increasing percentages of MeOH in CHCl₃ (0-3% MeOH/CHCl₃). Those fractions containing clean product are combined, concentrated under a N₂ stream, and pumped on high vacuum to give 14.

STEP O Preparation of 15 ##STR65##

To a stirred solution of 2.48 g di(p-nitrobenzyl)-ketomalonate (Step P) in 400 ml hot anhydrous toluene is added a solution of 2.52 g of 14 in 20 ml THF (distilled from LAH) and 40 ml anhydrous toluene. After some of the solvent is boiled off, additional anhydrous toluene is added, and the azeodrying process is repeated three times. The solution is then refluxed under N₂ for 30 minutes. Additional tolune is then allowed to boil off yet the volume is not allowed to diminish so much that precipitation occurs. Total heating time is approximately 21/2 hours. The clear yellow reaction mixture is removed from the oil bath and placed under a stream of N₂. After concentration to a oil, the residue is dissolved in CH₂ Cl₂, dried over anhydrous MgSO₄, filtered, and concentrated under a N₂ stream to give crude 15.

The material is chromatographed on 250 g silica gel packed and applied in CHCl₃ (height=43 cm; diameter=4.5 cm). Elution with 500 ml 0.5% MeOH/CHCl₃ is followed by continued elution with 1% MeOH/CHCl₃ for the remainder of the chromatography. After the emergence of excess reagent, those fractions containing pure 15 are combined, concentrated under a N₂ stream and then on high vacuum to give 15.

STEP P Preparation of di-p-Nitrobenzyl Ketomalonate ##STR66## A mixture of 100 g p-nitrobenzyl bromide (0.46 mole), 28.6 g malonic acid (0.275 mole) and 750 ml ethanol (EtOH) is stirred and warmed on the steam bath until solution is achieved. A solution of 33 g KOH in 200 ml of water is added carefully with swirling. An additional 200 ml of water is added, and the two-phase system is refluxed for 1.8 hours. The lighter color homogeneous solution is cooled in ice for 1 hour and the crude product isolated by filtration, washed twice with a minimum of cold EtOH, and dried by pulling dry N₂ through the cake; 33.7 g of solid is obtained. If, curing the refluxing stage the reaction mixture is slowly concentrated to ca. half volume by allowing refluxing solvent to distill off, the crude product yield rises to 77 g. The material is recrystallized from methanol to give pure di-p-nitrobenzyl malonate.

A mixture of 23.4 of di-p-nitrobenzyl malonate 10 g SeO₂, and 30-40 ml of xylene is stirred in a flask immersed in an oil bath The bath temperature is raised over 1 hour to 130°-135°. A gradual darkening of the reaction mixture is noted, and after a total of 4 hours at 130°-135°, most of the insoluble residue is black Se°. The mixture is cooled, MgSO₄ is added to remove the water, and Celite is added to aid in filtration. The mixture is filtered through Celite and the cake washed with xylene and a small portion of EtOAc. Final volume: 60 ml. A 100 g column of Baker silica gel is prepared in benzene and 10 ml of filtrate applied, then eluted with increasing amount of EtOAc in benzene, 500 ml fractions being collected. After one 2% ethyl acetate (EtOAc)/φH, and two 10% EtOAc/φH fractions, the third 10% and first 20% EtOAc/φH provide the bulk of the product (1.6 g from 10 ml filtrate) and judged by tlc (20% EtOAc/CHCl₃ ; silica gel GF). Recrystallization from benzene, (1 g in ca. 50 ml concentrated to 7/8 volume and "spiked" with 1 ml of H₂ O saturated benzene): provides di-p-nitrobenzyl ketomalonate.

STEP Q Preparation of 17: ##STR67##

A solution of 1.468 g of 15 in CH₂ Cl₂ is dried over anhydrous MgSO₄, filtered, and concentrated under a N₂ stream, and dried further under high vacuum just prior to the following reaction. To a solution of 15 in 24 ml THF (freshly distilled from LAH) at -20° C. is added 0.206 ml anhydrous pyridine. With stirring under N₂, 294 mg of freshly distilled thionyl chloride in 5 ml THF is added dropwise. The reaction mixture is stirred for 10 minutes at -20° C., then 1/2 hour at 0° C. and finally 1 hour at 25° C. The pyridine hydrochloride is filtered under N₂ and washed with 20 ml THF. The filtrate is concentrated under N₂ stream followed by pumping on high vacuum.

To this freshly prepared chloro compound is added with stirring a freshly shaken suspension of 678 mg tributylphosphine in 36.5 ml 9:1 DMF-H₂ O followed by 294 mg K₂ HPO₄. The reaction mixture is stirred at 25° C., for 35 minutes. After dilution with 120 ml EA and 60 ml brine, the layers are separated, and the aqueous one is extracted two times with EA. The combined organic layers are washed one time with brine, dried over anhydrous MgSO₄, filtered and concentrated under a N₂ stream followed by pumping on high vacuum to give crude 17.

The material is chromatographed on 100 g silica gel (height=28.5 cm; d=4 cm) packed and applied in CHCl₃ and eluted with 0.5% MeOH in CHCl₃. Those fractions containing clean product are combined, concentrated under a N₂ stream and then on high vacuum to give 17. (EA=ethyl acetate.)

STEP R Preparation of 19: ##STR68##

To 8.5 ml pentane (dried over 4 A Linde molecular sieves) is added 0.2 ml Br₂. To 0.706 g of 17 in 18 ml THF (freshly distilled from LAH) and 5.7 ml Et₂ O (dried over 3 A 1/16" Linde molecular sieves) at 0° C. under N₂ with stirring is added dropwise 1.8 ml of the above 0.45 M Br₂ solution (0.81 mmole) to give dibromide 18. After 15 minutes at 0° C., 0.42 ml triethylamine is added immediately followed by 10.5 ml ice-cold DMF (distilled from CaSO₄ at 40 mm and stored over 4 A Linde molecular sieves). The ice-bath is removed, and stirring at room temperature is continued for 2 hours. The reaction mixture is poured into a stirred, ice-cold mixture of 2.1 ml 1 M KH₂ PO₄ -70 ml H₂ O-100 ml EA. The layers are separated, and the aqueous one is saturated with NaCl and re-extracted with EA. The combined organic layers are washed once with brine, dried over anhydrous MgSO₄, and filtered. The filtrate is concentrated under a N₂ stream and then pumped on high vacuum to give crude 19.

The material is chromatographed on 60 g silica gel (diameter=2.8 cm) packed and applied in CHCl₃ and is eluted with 100 ml-2% EA/CHCl₃ ; 100 ml-4% EA/CHCl₃ and then 5% EA/CHCl₃ for the remainder of the chromatography. The fractions containing pure 19 are combined, concentrated under a N₂ stream, and pumped on high vacuum to give 19.

STEP S Preparation of 20 ##STR69##

To 29 mg anhydrous silver fluoride is added a solution of 146 mg of 19 in 3.5 ml anhydrous pyridine. The stoppered reaction mixture is stirred at room temperature in the dark for one hour and then poured into 20 ml cold water-30 ml EA. After separation of the layers, the aqueous one is extracted two times with EA and one time with CHCl₃. Each organic layer is extracted one time with H₂ O and one time with brine. The combined organic layers are dried over anhydrous MgSO₄, filtered, and concentrated under a N₂ stream followed by pumping on high vacuum to give crude 20.

Preparation thin layer chromatography (eluant=40% acetone/hexane; repeated extraction of desired u.v. band with a large volume of CHCl₃) yields slightly contaminated 20. Re-chromatographing on silica using EA in CHCl₃ as an eluting system gives pure 20.

STEP T Preparation of 21: ##STR70##

A solution of 77 mg of 20 in 0.9 ml S-collidine (distilled from powdered KOH) is added to 13.4 mg anhydrous LiI (dried for few hours at 100° C. over P₂ O₅ under vacuum). With stirring under N₂, the reaction mixture is heated in an oil bath at 120° C. After a total of 30 minutes, the reaction mixture is cooled to 25° C., diluted with CH₂ Cl₂, and transferred to a round bottom flask for concentration under a N₂ stream and then on high vacuum. Partitioning the residue between EA-H₂ O and 1 ml 1 M KH₂ PO₄ is followed by extraction of the aqueous layer two additional times with EA and one time with CHCl₃. Each organic layer is then backwashed with brine. The combined organic layers are dried over anhydrous MgSO₄ filtered, concentrated under a N₂ stream and then on high vacuum to give crude 21.

Preparative thin layer chromatography on silica gel yields 21.

STEP U Preparation of 22: ##STR71##

To 49 mg of 21 in 0.7 ml DMSO (distilled from CaH₂ at 8 mm and stored over 4 A Linde molecular sieves) is added 100 μl diisopropylamine (distilled from NaH under N₂ and stored over 4 A Linde molecular sieves). The stoppered reaction mixture is stirred for a few minutes and then allowed to stand for 2 hours. The amine and most of the DMSO are then concentrated off under high vacuum with no external heating. The residue is passed quickly through a column of silica gel (packed, applied and eluted with EA) to remove residual DMSO. After concentration under a N₂ stream of all fractions having u.v. absorbance, the material is chromatographed on a thin layer silica gel plate (eluant=50% EA/CHCl₃ ; repeated extraction of desired u.v. bands with a large volume of chloroform) to give 22.

STEP V Preparation of I: ##STR72##

To 5.2 mg 22 is added 0.60 ml dioxane, 0.05 ml ethanol, 0.35 ml deionized water and 0.01 ml of 1.0 M K₂ HPO₄. To the resultant clear solution is added 5 mg of 10% Pd/C. The suspension is flushed with N₂, then 5-6 times alternately with 50 psi H₂ atmosphere for 30-40 minutes. After centrifugation, the Pd/C is washed and centrifuged 2-3X with 0.5 ml portions of deionized water. The combined centrifugates are extracted 5×1-2 ml ether. Residual ether is removed under vacuum and the aqueous solution is chromatographed on an XAD-2 column (20×140 mm) which is eluted with water to give the desired product I.

EXAMPLE 3 Preparation of Bis-(p-Nitrobenzyloxycarbonylamino-2-propyl)disulfide ##STR73## Under nitrogen at -20° C., bromide (1.21 ml, 0.022 mmole) is added to a solution of p-nitrobenzyloxycarbonylamino-2-propanethiol (11.28 g), in 100 ml of anhydrous tetrahydrofuran. The cooling bath is removed, and the cold solution is stirred for 15 minutes. The solution is then diluted with 400 ml ethyl acetate and washed with 200 ml 1 M pH 7 phosphate buffer, 200 ml 1 M dibasic potassium phosphate, water (2×200 ml, 100 ml) and 200 ml brine. It is dried over anhydrous magnesium sulfate and filtered. The filtrate is evaporated in vacuo giving a yellow solid residue. This material is chromatographed on silica gel eluting with 5% ethyl acetate/chloroform to give crystalline product. EXAMPLE 4

Following the procedure of Example 2, Steps A-Gb, the following substituted azetidinones 10 are obtained when an equivalent amount of the appropriately substituted butadiene reagent is substituted for the 1-acetoxyl-2-methyl-1,3-butadiene of Example 2, Step A. The following chart gives the final azetidinone product, the necessary reagents and any pertinent remarks:

    ______________________________________                                          ##STR74##                                                                                                      Butadiene                                                                      used in                                       Com-                             Example 2,                                    pound   R             R.sup.1    Step A                                        ______________________________________                                         (1.)                                                                                  ##STR75##      CH.sub.3 CH.sub.2                                                                          ##STR76##                                    (2.)                                                                                  ##STR77##      CH.sub.3 CH.sub.2 CH.sub.2                                                                 ##STR78##                                    (3.)                                                                                  ##STR79##                                                                                      ##STR80##                                                                                 ##STR81##                                    (4.)                                                                                  ##STR82##                                                                                      ##STR83##                                                                                 ##STR84##                                    (5.)                                                                                  ##STR85##      Ph                                                                                         ##STR86##                                    (6.)                                                                                  ##STR87##      PhCH.sub.2                                                                                 ##STR88##                                    ______________________________________                                    

EXAMPLE 5

Following the procedure of Example 2, Steps L-V, the following species of the present invention are obtained when the azetidinones 10 of Example 4 are substituted in equivalent amounts, respectively for the azetidinone of Example 2, Step A. The products of this Example are presented in tabular fashion below:

    ______________________________________                                          ##STR89##                                                                     Compound      R.sup.1         Remarks                                          ______________________________________                                         (1.)         CH.sub.3 CH.sub.2                                                 (2.)         CH.sub.3 CH.sub.2 CH.sub.2                                        (3.)                                                                                         ##STR90##                                                        (4.)                                                                                         ##STR91##                                                        (5.)                                                                                         ##STR92##                                                        (6.)                                                                                         ##STR93##                                                        ______________________________________                                    

EXAMPLE 6 Preparation of 8-oxo-2,2,5,7-tetramethyl-3-oxa-1-azabicyclo[4.2.0]octane ##STR94##

THF, (20 ml) is placed under N₂ treated with 1.54 ml diisopropylamine and cooled to -78° C. A solution of n-butyl lithium 1.97 M in hexane 5.6 ml is added dropwise over 5 min. The reaction mixture is stirred at -78° C. for 10 min and then treated with 8-oxo-2,2,5-trimethyl-3-oxa-1-azabicyclo[4.2.0]octane (1.55 g) in 15 ml THF added dropwise over 5 min. After another 10 min hexamethylphosphoramide 1.97 ml is added. The mixture is stirred another 10 min, then treated with 2 ml of methyl iodide. The reaction mixture is stirred at -78° for 154 min and allowed to warm to 25° C. and stirred for 15 min. The reaction mixture is diluted with EtOAc, washed once with pH 7 phosphate buffer and dried and evaporated. The residue is chromatographed on silica gel using 25% EtOAc/C.sub. 6 H₆ as eluant to give 8-oxo-2,2,5,7-tetramethyl-3-oxa-1-azabicyclo[4.2.0]octane.

EXAMPLE 7 Preparation of 8-oxo-2,2,5,7-tetramethyl-7-(hydroxymethyl)-3-oxa-1-azabicyclo[4.2.0]octan ##STR95##

To a solution of 1.1 equivalents of freshly prepared lithium diisopropylamide in anhydrous tetrahydrofuran under a nitrogen atmosphere at -78° is added a solution of 8-oxo-2,2,5,7-tetramethyl-3-oxa-1-azabicyclo[4.2.0]octane in anhydrous tetrahydrofuran which has been cooled to -78° C. After two minutes, the resulting lihtium enolate is treated with excess formaldehyde, introduced as a gas just above the surface of the stirred solution. The solution is stirred for 30 minutes at -78° and then poured into water. The aqueous phase is saturated with sodium chloride and extracted with ethyl acetate. The combined ethyl acetate solutions are dried over magnesium sulfate and filtered. The filtrate is evaporated under reduced pressure to give the crude product. Purification by chromatography on silica gel using ethyl acetate/benzene gives 8-oxo-2,2,5,7-tetramethyl-7-(hydroxymethyl)-3-oxa-1-azabicyclo[4.2.0]-octane.

EXAMPLE 8 Preparation of 8-Oxo-2,2,5,7-tetramethyl-7-(p-nitrobenzylcarbonyldioxymethyl)-3-oxa-1-azabicyclo[4.2.0]octane ##STR96##

Under anhydrous conditions at 0° C. a solution of 8-oxo-2,2,5,7-tetramethyl-7-(hydroxymethyl)-3-oxa-1-azabicyclo[4.2.0]octane (60 mg) in 0.6 ml ether is treated with powdered potassium hydroxide (19 mg). After a period of 15 minutes, p-nitrobenzyl chloroformate (65 mg) is added to the reaction mixture. Stirring is continued at 25° C. for an additional 15 hours. The mixture is partitioned between 1 M pH 7 phosphate buffer and more ether. The phase is washed with water and brine, dried over magnesium sulfate and filtered. Evaporation of the filtrate under reduced pressure gives 67 mg of a colorless oil. Purification by preparative thick-layer chromatography on silica gel developing with 1:9 ethyl acetate/benzene gives 8-oxo-2,2,5,7-tetramethyl-7-(p-nitrobenzylcarbonyldioxymethyl)-3-oxa-1-azabicyclo[4.2.0]octane as a mixture of diastereomers.

EXAMPLE 9 Preparation of 3-methyl-3-(p-nitrobenzylcarbonyldioxymethyl)-4-(1-methyl-2-hydroxyethyl)-2-azetidinone ##STR97## 8-Oxo-3-oxa-2,2,5,7-tetramethyl-7-(1-p-nitrobenzylcarbonyldioxymethyl)-1-azabicyclo[4.2.0]octane (1.0 g) is dissolved in 8 ml trifluoroacetic acid and 8 ml water and heated at 25° C. for 15 min. The reaction mixture is neutralized with KHCO₃, and then extracted with EtOAc. The organic layer is separated, dried over MgSO₄ and evaporated in vacuo. The residue is taken up in benzene and evaporated to give 3-methyl-3-(p-nitrobenzylcarbonyldioxymethyl)-4-(1-methyl-2-hydroxyethyl)-2-azetidinone as a mixture of diastereoisomers. EXAMPLES 10-13 Examples 10, 11, 12, and 13 complement Examples 6, 7 8 and 9 for the preparation of 3-methyl-3-(p-nitrobenzylcarbonyldioxymethyl)-4-(1-methyl-2-hydroxyethyl)-2-azetidinone ##STR98## EXAMPLE 10 Preparation of 1-(2-Tetrahydropyranyl)-3-methyl-4-[1-methyl-2-(2-tetrahydropyranyl)oxyethyl]-2-azetidinone ##STR99## Under nitrogen and at 25° C., a solution of 3-methyl-4-(1-methyl-2-hydroxyethyl)-2-azetidinone (62 mg) in 0.5 ml of anhydrous p-dioxane is treated with 2,3-dihydropyran (0.98 ml) and p-toluenesulfonic acid monohydrate (19 mg). The resulting solution is stirred for a period of 60 minutes and then partitioned between 10 ml of 0.5 M pH 7 phosphate buffer and 10 ml of ethyl acetate. The aqueous phase is extracted a second time with ethyl acetate. The combined ethyl acetate solutions are washed with brine, dried over magnesium sulfate and filtered. The filtrate is evaporated under reduced pressure to give 216 mg of crude product. Purification by preparative thick-layer chromatography developing with ethyl acetate gives 80 ml of 1-(2-tetrahydropyranyl)-3-methyl-4-[1-methyl-2-(2-tetrahydropyranyl)-oxyethyl]-2-azetidinone as an oil. EXAMPLE 11 Preparation of 1-(2-tetrahydropyranyl)-3-methyl-3-(1-hydroxymethyl)-4-[1-methyl-2-(2-tetrahydropyranyl)-oxyethyl]-2-azetidinone ##STR100## Following the procedure described for the preparation of 8-oxo-2,2,5,7-tetramethyl-7-(hydroxymethyl)-3-oxa-1-azabicyclo[4.2.0]octane from 8-oxo-2,2,5,7-tetramethyl-3-oxa-1-azabicyclo[4.2.0]octane (Example 6, above) and using 3-methyl-1-(2-tetrahydropyranyl)-4-[1-methyl-2-(2-tetrahydropyranyl)-oxyethyl]-2-azetidinone one obtains a diastereomeric mixture of 1-(2-tetrahydropyranyl)-3-methyl-3-(hydroxymethyl)-4[1-methyl-2-(2-tetrahydropyranyl)-oxyethyl]-2-azetidinone. EXAMPLE 12 Preparation of 3-Methyl-1-(2-tetrahydropyranyl)-3-(1-p-nitrobenzylcarbonyldioxymethyl)-4-[1-methyl-2-(2-tetrahydropyranyl)oxyethyl]-2-azetidinone ##STR101## Following the procedure described for the preparation of 8-oxo-2,2,5,7-tetramethyl-7-(1-p-nitrobenzylcarbonyldioxymethyl)-3-oxa-1-azabicyclo[4.2.0]octane from 8-oxo-2,2,5,7-tetramethyl-(1-hydroxymethyl)-3-oxa-1-azabicyclo[4.2.0]octane and using 3-methyl-1-(2-tetrahydropyranyl)-3-(hydroxymethyl)-4-[1-methyl-2-(2-tetrahydropyranyl)oxyethyl]-2-azetidinone there is obtained 3-methyl-1-(2-tetrahydropyranyl)-3-(p-nitrobenzylcarbonyldioxymethyl)-4-[1-methyl-2-(2-tetrahydropyranyl)oxyethyl]-2-azetidinone. EXAMPLE 13 Preparation of 3-Methyl-3-(p-nitrobenzylcarbonyldioxymethyl)-4-(1-methyl-2-hydroxyethyl)-2-azetidinone ##STR102## A solution of 3-methyl-1-(2-tetrahydropyranyl)-3-(p-nitrobenzylcarbonyldioxymethyl)-4-[1-methyl-2-(2-tetrahydropyranyl)oxyethyl]-2-azetidinone in methanol at 25° C. is treated with 0.1 molar equivalent of p-toluenesulfonic acid monohydrate. The solution is stirred for a period of 2 hours and then neutralized with 1 M pH 7 phosphate buffer. The product is extracted into ethyl acetate. The ethyl acetate solution is washed with brine, dried over magnesium sulfate and filtered. The filtrate is evaporated under reduced pressure to give 3-methyl-3-(p-nitrobenzylcarbonyldioxymethyl)-4-(1-methyl-2-hydroxyethyl)-2-azetidinone. EXAMPLE 14 Preparation of 1,6-dimethyl-2-(2-aminoethylthio)-6-(hydroxymethyl)-1-carbadethiapen-2-em-3-carboxylic acid Step A Preparation of 12' ##STR103## To 6.75 ml anhydrous pyridine in 350 ml anhydrous acetonitrile is added 4.05 g anhydrous powdered chromium trioxide. After stirring at room temperature (25° C.) for 30 minutes, 9.6 g dried Supercell is added and stirring is continued for 5 additional minutes. A solution fo 3.21 g 3-methyl-3-(p-nitrobenzylcarbonyldioxymethyl)-4-(1-methyl-2-hydroxyethyl)-2-azetidinone in 30 ml anhydrous acetonitrile is added all at once. The reaction mixture is stirred under anhydrous conditions at room temperature (25° C.) for one hour. Addition of 9.6 g NaHSO₃ is followed by 5 minutes of stirring after which the reaction mixture is filtered through a mixed packed bed of 40 g silica gel and 40 g anhydrous magnesium sulfate. The bed is washed repeatedly with acetontrile (total volume of filtrate 600 ml). The filtrate is concentrated under a N₂ stream to 130 ml total volume. To this solution containing crude aldehyde at 0° C. under N₂ is added 9.64 g p-nitrobenzyloxycarbonylaminoethanethiol as prepared below (Example 14, Step B). To the stirred reaction mixture is added 8.0 ml boron trifluoride etherate. After 1.5 hours at 0° C., the reaction mixture is poured into a stirred ice-cold mixture of 69 g K₂ HPO₄ -500 ml H₂ O and 700 ml ethyl acetate (EA). The layers are separated, and the aqueous one is saturated with NaCl and re-extracted with additional EA. The combined organic layers are washed twice with brine, dried over anhydrous MgSO₄ and filtered. The filtrate is concentrated under a N₂ stream and then pumped on high vacuum to give crude 12'.

The material is chromatographed on 450 g silica gel (column hieght=48 cm; diameter=5.5 cm) packed and applied in CHCl₃ and eluted with increasing percentages of MeOH in CHCl₃ (0-4% MeOH/CHCl₃). Those fractions containing the desired product are combined, concentrated under a N₂ stream; and pumped on high vacuum to give 12'.

STEP B Preparation of p-Nitrobenzyloxycarbonylaminoethanethiol ##STR104## To 600 ml diethyl ether (Et₂ O) - 75 ml H₂ O in an ice bath with stirring is added 3.2 g cysteamine hydrochloride (mw=114; 28.1 mmole). A solution of 7.14 g NaHCO₃ (mw=84; 85 mmole) in 75 ml H₂ is added. The ice bath is removed and at room temperature a solution of 6.75 g p-nitrobenzylchloroformate (mw=216; 31.3 mmole) in 270 ml of Et₂ O is added dropwise over a period of one hour. After 10 additional minutes, the layers are separated. The ether layer is extracted with 150 ml of 0.25 NHCl, and then with 200 ml brine. Each aqueous layer is then backwashed successively with 100 ml ET₂ O. The combined Et₂ O layers are dried over anhydrous MgSO₄, filtered, and concentrated under a N₂ strea. The crystalline residue is slurried in a small amount of ether, filtered, and the pale yellow crystals are dried under high vacuum to give 4.7 g p-nitrobenzyloxycarbonylaminoethanethiol (65% yield). NMR (CDCl₃) 8.18 (d, J=8 Hz, aromatic protons ortho to nitro), 7.47 (d, J=8 Hz, aromatic protons meta to nitro), 5.27 (--NH--), 5.20 (s, --CH₂ --φ-pNO₂), 3.40 (m, --CH₂ --NH--), 2.67 (m, --CH₂ --SH), 1.35 (t, J=8.5 Hz, --SH) in ppm downfield from TMS.

IR(CHCl₃ solution) carbonyl- 1725 cm⁻¹

M.S. - molecular ion-256, (M-47) at 209, (M, 136) at 120 +CH₂ φpNO₂ at 136.

STEP C Preparation of 14' ##STR105##

To 14.2 ml pentane (dried over 4A Linde molecular sieves) is added 0.5 ml Br₂. To 5 g of 12' in 58 ml tetrahydrofuran (THF) (freshly distilled from lithium aluminum hydride) (LAH) and 65 ml Et₂ O (dried over 3A 1/16" Linde molecular sieves) at 0° C. under N₂ with stirring is added dropwise 10 ml of the above 0.66 M Br₂ solution. After 10 minutes at 0° C., 0.67 ml cyclohexane is added. After 5 minutes at 0° C., 1.7 ml triethylamine is added immediately followed by 40 ml ice-cold dimethylformamide (DMF) (distilled from anhydrous CaSO₄ at 40 mm and stored over 4A Linde molecular sieves). The ice bath is removed, and stirring is continued for 21/4 hours at room temperature. The reaction mixture is poured into a stirred ice-cold mixture of 12.6 ml 1 M KH₂ PO₄ 160 ml H₂ O - 500 (EA). After separation of the layers, the aqueous one is saturated with sodium chloride and re-extracted with EA. The combined organic layers are extracted once with brine, dried over anhydrous MgSO₄, filtered and concentrated under N₂ stream followed by pumping under high vacuum to provide crude 14'.

The material is chromatographed on 250 g silica gel (height=45 cm; diameter=4.5 cm) packed and applied in CHCl₃ and eluted with increasing percentages of MeOH in CHCl₃ (0-3% MeOH/CHCl₃). Those fractions containing clean product are combined, concentrated under a N₂ stream, and pumped on high vacuum to give 14'.

STEP D Preparation of 15' ##STR106##

To a stirred solution of 2.48 g di(p-nitrobenzyl)ketomalonate in 400 ml hot anhydrous toluene is added a solution of 2.52 g of 14' in 20 ml THF (distilled from LAH) and 40 ml anhydrous toluene. After some of the solvent is boiled off, additional anhydrous toluene is added, and the azeodrying process is repeated three times. The solution is then refluxed under N₂ for 30 minutes. Additional toluene is then allowed to boil off yet the volume is not allowed to diminish so much that precipitation occurs. Total heating time is approximately 21/2 hours. The clear yellow reaction mixture is removed from the oil bath and placed under a stream of N₂ which instantaneously causes clouding. After concentration to a yellow oil, the residue is dissolved in CH₂ Cl₂, dried of anhydrous MgSO₄, filtered, and concentrated under a N₂ stream to give crude 15'.

The material is chromatographed on 250 g silica gel packed and applied in CHCl₃ (height=43 cm; diameter=4.5 cm). Elution with 500 ml 0.5% MeOH/CHCl₃ is followed by continued elution with 1% MeOH/CHCl₃ for the remainder of the chromatography. After the emergence of excess reagent, those fractions containing pure 15' are combined, concentrated under a N₂ stream and then on high vacuum to give 15'.

STEP E Preparation of 17' ##STR107##

A solution of 1.468 g of 15' in CH₂ Cl₂ is dried over anhydrous MgSO₄, filtered, concentrated under a N₂ stream, and dried further under high vacuum just prior to the following reaction. To a solution of 15' in 24 ml THF (freshly distilled from LAH) at -20° C. is added 0.206 ml anhydrous pyridine. With stirring under N₂ 294 mg of freshly distilled thionyl chloride in 5 ml THF is added dropwise. The reaction mixture is stirred for 10 minutes at -20° C., the 1/2 hour at 0° C. and finally 1 hour at 25° C. The pyridine hydrochloride is filtered under N₂ and washed with 20 ml THF. The filtrate is concentrated under N₂ stream followed by pumping on high vacuum.

To this freshly prepared chloro compound is added with stirring a freshly shaken suspension of 678 mg tributylphosphine in 36.5 ml 9:1 DMF - H₂ O followed by 294 mg K₂ HPO₄. The reaction mixture is stirred at 25° C., for 35 minutes. After dilution with 120 ml EA and 60 ml brine, the layers are separated, and the aqueous one is extracted two times with EA. The combined organic layers are washed one time with brine, dried over anhydrous MgSO₄, filtered and concentrated under a N₂ stream followed by pumping on high vacuum to give crude 17'.

The material is chromatographed on 100 g silica gel (height=28.5 cm; d=4 cm) packed and applied in CHCl₃ and eluted with 0.5% MeOH in CHCl₃. Those fractions containing clean product are combined, concentrated under a N₂ stream and then on high vacuum to give 17'.

STEP F Preparation of 19' ##STR108##

To 8.5 ml pentane (dried over 4A Linde molecular sieves) is added 0.2 ml Br₂. To 0.706 g of 17' in 18 ml THF (freshly distilled from LAH) and 5.7 ml Et₂ O (dried over 3A 1/16" Linde molecular sieves) at 0° C. under N₂ with stirring is added dropwise 1.8 ml of the above 0.45 M Br₂ solution. After 15 minutes at 0° C., 0.42 ml triethylamine is added immediately followed by 10.5 ml ice-cold DMF (distilled from CaSO₄ at 40 mm and stored over 4A Linde molecular sieves). The ice-bath is removed, and stirring at room temperature is continued for 2 hours. The reaction mixture is poured into a stirred ice-cold mixture of 3.1 ml 1 M KH₂ PO - 70 ml H₂ O - 100 ml EA. The layers are separated, and the aqueous one is saturated with NaCl and re-extracted with EA. The combined organic layers are washed once with brine, dried over anhydrous MgSO₄, and filtered. The filtrate is concentrated under a N₂ stream and then pumped on high vacuum to give crude 19'.

The material is chromatographed on 60 g silica gel (diameter=2.8 cm) packed and applied in CHCl₃ and is eluted with 100 ml - 2% EA/CHCl₃ ; 100 ml - 4% EA/CHCl₃ and then 5% EA/CHCl₃ for the remainder of the chromatography. The fractions containing pure 19' are combined, concentrated under a N₂ stream, and pumped on high vacuum to give 19'.

STEP G PREPARATION OF 20' ##STR109##

To 29 mg anhydrous silver fluoride is added a solution of 146 mg of 19' in 3.5 ml anhydrous pyridine. The stoppered reaction mixture is stirred at room temperature in the dark for one hour and then poured into 20 ml cold water - 30 ml EA. After separation of the layers, the aqueous one is extracted two times with EA and one time with CHCl₃. Each organic layer is extracted one time with H₂ O and one time with brine. The combined organic layers are dried over anhydrous MgSO₄, filtered, and concentrated under a N₂ stream following by pumping on high vacuum to give crude 19'.

Preparative thin layer chromatograph (eluant=40% acetone/hexane; repeated extraction of desired u.v. band with a large volume of HCCl₃) yields slightly contaminated 20'. Re-chromatographing on silica gel using EA in CHCl₃ as an eluting system gives 20'.

STEP H Preparation of 21' ##STR110## A solution of 77 mg of 20' in 0.9 ml S-collidine (distilled from powdered KOH) is added to 13.4 mg anhydrous LiI (dried for few hours at 100° C. over P₂ O₅ under vacuum). With stirring under N₂, the reaction mixture is heated in an oil bath at 120° C. After a total of 30 minutes, the reaction mixture is cooled to 25° C., diluted with CH₂ Cl₂, and transferred to a round bottom flask for concentration under a N₂ stream and then on high vacuum. Partitioning the residue between EA-H₂ O and 1 ml 1 M KH₂ PO₄ is followed by extraction of the aqueous layer two additional times with EA and one time with CHCl₃. Each organic layer is then backwashed with brine. The combined organic layers are dried over anhydrous MgSO₄, filtered, concentrated under a N₂ stream and then on high vacuum to give crude 21'.

Preparative thin layer chromatography on silica gel (plate is eluted two times with 40% acetone/hexane; repeated extraction of the appropriate u.v. bands with large volume of CHCl₃) yields 21'.

STEP I Preparation of 22' ##STR111## To 49 mg of 21' in 0.7 ml DMSO (distilled from CaH₂ at 8 mm and stored over 4A Linde molecular sieves) is added 100 μl diisopropylamine (distilled from NaH under N₂ and stored over 4A Linde molecular sieves). The stoppered reaction mixture is stirred for a few minutes and then allowed to stand for 2 hours. The amine and most of the DMSO are then concentrated off under high vacuum with no external heating. The residue is passed quickly through a column of silica gel (packed, applied, and eluted with EA) to remove residual DMSO. After concentration under a N₂ stream of all fractions having u.v. absorbance, the material is chromatographed on a thin layer silica gel plate (eluant=50% EA/CHCl₃ ; repeated extraction of desired u.v. bands with a large volume of chloroform) to give 22'. STEP J Preparation of (I) ##STR112## To 5.2 mg 22' is added 0.60 ml dioxane, 0.05 ml ethanol, 0.35 ml deionized water and 0.01 ml of 1.0 M K₂ HPO₄. To the resultant clear solution is added 5 mg of 10% Pd/C. The suspension is flushed with N₂, then 5-6 times alternately with 50 psi H₂ and vacuum. Finally, it is shaken under a 50 psi H₂ atmosphere for 30-40 min. After centrifugation, the Pd/C is washed and centrifuged 2-3X with 0.5 ml portions of deionized water. The combined centrifugates are extracted 5×1 - 2 ml ether. Residual ether is removed under vacuum and the aqueous solution applied to an XAD-2 column (20×140 mm). Fractions of 100 drops (6-7 ml) are collected, with continuous UV monitoring, by elution with deionized water to give (I). EXAMPLE 15 Preparation of Bis (p-Nitrobenzyloxycarbonylaminoethyl)disulfide ##STR113## Under nitrogen at -20° C. bromine (1.21 ml, 0.022 mmole) is added to a solution of p-nitrobenzyloxycarbonylaminoethanethiol (11.28 g, 0.044 mole) in 100 ml of anhydrous tetrahydrofuran. The cooling bath is removed, and the cold solution is stirred for 15 minutes. The solution is then diluted with 400 ml ethyl acetate and washed with 200 ml 1 M pH 7 phosphate buffer, 200 ml 1 M dibasic potassium phosphate, water (2×200 ml, 100 ml) and 200 ml brine. It is dried over anhydrous magnesium sulfate and filtered. The filtrate is evaporated in vacuo giving a yellow solid residue. This material is chromatographed on silica gel eluting with 50% ethylacetate/chloroform to give 10.5 g of crystalline bis (p-nitrobenzyloxycarbonylaminoethyl)disulfide:

    ______________________________________                                         IR (CH.sub.2 Cl.sub.2) μ:                                                             3.04          NH                                                               5.96          carbonyl                                                         6.22,         6.61 nitro                                             NMR (CDCl.sub.3):                                                                        8.24                                                                                          d, J = 8.5Hz, ArH                                               7.54                                                                           5.37,         broad s, HN                                                      5.26,         s, ArCH.sub.2 O                                                  3.60,         q, J = 6Hz and 6Hz, NHCH.sub.2 CH.sub.2                          2.86,         t, J = 6Hz, NHCH.sub.2 CH.sub.2 S                      ______________________________________                                    

EXAMPLE 16 Preparation of 8-oxo-2,2,5,-trimethyl-7α and β-hydroxymethyl-3-oxo-1-azabicyclo[4.2.0]octane ##STR114## The procedure of Example 7, substituting 8-oxo-2,2,5-trimethyl-3-oxa-1-azabicyclo[4.2.0]octane for 8-oxo-2,2,5,7-tetramethyl-3-oxa-1-azabicyclo[4.2.0]octane, is carried out. Upon purification by silica gel chromatography, the title compound is obtained. EXAMPLE 17 Preparation of 1-methyl-2-(2-aminoethylthio)-6-hydroxymethyl-1-carbadethiapen-2-em-3-carboxylic acid ##STR115## Following the procedure described above for the preparation of 1,6-dimethyl-2-(2-aminoethylthio)-6-hydroxymethyl-1-carbadethiapen-2-em-3-carboxylic acid, except that in Example 8 an equivalent amount of 8-oxo-2,2,5-trimethyl-7-hydroxymethyl-3-oxa-1-azabicyclo[4.2.0]octane rather than the 2,2,5,7-tetramethyl species is taken; the tile compound is obtained when the procedures of Examples 8, 9 and 14 are followed. EXAMPLE 18 Preparation of 8-oxo-2,2,5-trimethyl-7α and β-(1-hydroxy-2-phenylethyl)-3-oxa-1-azabicyclo[4.2.0]-octane ##STR116## Following the procedure of Example 2, Step Fa except that instead of acetaldehyde, an equivalent amount of phenylacetaldehyde is used, upon purification by silica gel chromatography, the title compound is obtained. EXAMPLE 19 Preparation of 1-methyl-(2-aminoethylthio)-6-(1-hydroxy-2-phenylethyl)-1-carbadethiapen-2-em-3-carboxylic acid ##STR117## Following the procedure of Example 8 except that 8-oxo-2,2,5-trimethyl-7-(1-hydroxy-2-phenylethyl)-3-oxa-1-azabicyclo[4.2.0]octane is substituted in equivalent amount for its analogous substrate, the title compound is obtained. EXAMPLE 20 Preparation of 8-oxo-2,2,5-trimethyl-7α-benzyl-3-oxa-1-azabicyclo[4.2.0]octane ##STR118## Following the procedure of Example 6 and using benzyl bromide instead of methyl iodide there is obtained 8-oxo-2,2,5-trimethyl-7α-benzyl-3-oxa-1-azabicyclo[4.2.0]octane. EXAMPLE 21 Preparation of 8-oxo-2,2,5-trimethyl-7α and β-benzyl-7β and α-(1-hydroxyethyl)-3-oxa-1-azabicyclo[4.2.0]octane ##STR119## Using the procedure of Example 7 but substituting an equivalent amount of 8-oxo-2,2,5-trimethyl-7α-benzyl-3-oxa-1-azabicyclo[4.2.0]octane (Example 20) for 8-oxo-2,2,5,7-tetramethyl-3-oxa-1-azabicyclo[4.2.0], and an equivalent amount of acetaldehyde for formaldehyde, there is obtained, upon purification by silica gel chromatography, the title compounds. EXAMPLE 22 Preparation of 8-oxo-2,2,5-trimethyl-7α(1-mesyloxyethyl)-3-oxa-1-azabicyclo[4.2.0]octane ##STR120## Under nitrogen at 0° a solution of 8-oxo-2,2,5-trimethyl-7, 1-hydroxyethyl-3-oxa-1-azabicyclo[4.2.0]octane (128 mg) and triethylamine (134 μl) in 5 ml of sieve dried methylene chloride is treated with redistilled methane sulfonyl chloride (55 μl). The resulting solution is stirred for 30 minutes. It is then washed with 10 ml each of cold water, 1 molar pH 3 phosphate buffer, 5% sodium bicarbonate, water and finally brine. The organic phase is dried over magnesium sulfate and filtered. The filtrate is evaporated in vacuo to give the crude product. This material is chromatographed on preparative thick layer silica gel plates developed with acetone/hexane to give a separated diastereomeric mesylate. EXAMPLE 23 Preparation of 8-oxo-2,2,5-trimethyl-7α-(1-azidoethyl)-3-oxa-1-azabicyclo[4.2.0]octane ##STR121## A solution of lithium azide, prepared by stirring over night a mixture of 170 mg sodium azide and 100 mg lithium chloride in 3 ml of anhydrous dimethyl sulfoxide, followed by filtration, is added to 160 mg of 8-oxo-2,2,5-trimethyl-7α(1-mesyloxyethyl)-3-oxa-1-azabicyclo[4.2.0]octane and stirred under nitrogen at 25° C. for eight hours. The mixture is then poured into 10 ml ice water and extracted with ethyl acetate, the combined extracts washed once with water, once with saturated sodium chloride solution, dried (MgSO₄) and evaporated under a nitrogen stream. The crude product is purified by preparative tlc to afford the title compound. EXAMPLE 24 Preparation of 8-oxo-2,2,5-trimethyl-7α-(1-p-nitrobenzyloxycarbonylaminoethyl)-3-oxa-1-azabicyclo[4.2.0]octane ##STR122## A mixture of 107 mg of 8-oxo-2,2,5-trimethyl-7α-(1-azidoethyl)-3-oxa-1-azabicyclo[4.2.0]octane and 50 mg of 10% Pd/C in 2 ml of anhydrous dioxane is shaken under 3 atmospheres of hydrogen for 1.5 hours. The mixture is filtered and concentrated to 1 ml under a nitrogen stream, then treated with 1 ml of 1 M K₂ HPO₄ and 1 ml methylene chloride. The mixture is stirred vigorously in an ice bath under nitrogen while a solution of 120 mg of p-nitrobenzylchloroformate in 0.5 ml methylene chloride is added dropwise over one minute. The solution is stirred for another 15 minutes, then treated with 0.1 ml pyridine in 2 ml water and stirred vigorously for another 15 minutes. The organic phase is removed and the aqueous phase is extracted several more times with methylene chloride. The combined organic phases are washed twice with water, once with saturated NaCl, dried (MgSO₄) and evaporated under reduced pressure. Purification by preparative tlc affords the title compound. EXAMPLE 25 Preparation of 8-oxo-2,2,5-trimethyl-7(1-o-nitrobenzylthioethyl)-3-oxa-1-azabicyclo[4.2.0]octane ##STR123## When in Example 23 an equivalent solution of o-nitrobenzyl mercaptan in DMF is substituted for the lithium azide solution, the title compound is obtained. EXAMPLE 26 Preparation of 4-(1-methyl-2,2-bisbenzylthioethyl)-3-methyl-3(p-nitrobenzylcarbonyldioxymethyl)-2-azetidinone ##STR124## When in Example 14, Step A, an equivalent amount of benzyl mercaptan is substituted for 2-(p-nitrobenzyloxycarbonylamino)ethane thiol, the title compound is obtained. EXAMPLE 27 Preparation of 3-methyl-4-[1-methyl-2,2-bis-(1',1'-dimethyl-p-nitrobenzoxycarbonylaminoethylthio]-3-(p-nitrobenzylcarbonyldioxymethyl)-2-azetidinone ##STR125## When in Example 14, Step A, an equivalent amount of 2-(p-nitrobenzyloxycarbonylamino)-1,1-dimethylethanethiol is substituted for 2-(p-nitrobenzyloxycarbonylamino)ethane thiol, the title compound is obtained. EXAMPLE 28 Preparation of 1,6-dimethyl-2-benzylthiohydroxymethyl-1-carbadethiapen-2-em-3-carboxylic acid ##STR126## Following the procedure of Example 14, Steps A-K, except substituting for the indicated azetidinone the azetidinone of Example 26, the title compound is obtained. EXAMPLE 29 Preparation of 1,6-dimethyl-2-(2-amino-1,1-dimethylethylthio)-6-(1-hydroxymethyl)-1-carbadethiapen-2-em-3-carboxylic acid ##STR127## Following the procedure of Example 14, step A-K, except substituting for the indicated azetidinone the azetidinone of Example 27, the title compound is obtained. EXAMPLE 30

Following the procedure of the foregoing Examples and text, the following representative compounds of the present invention (Table I) are obtained by analogy.

    __________________________________________________________________________      ##STR128##                                                                    Com-                                                                           pound                                                                              R.sup.8      R.sup.6                                                                           R.sup.7                                                                              R.sup.1                                                                              Remarks                                        __________________________________________________________________________     1.  (CH.sub.2).sub.3 NH.sub.2                                                                   H  CH.sub.2 OH                                                                          CH.sub.3                                                                             HS(CH.sub.2).sub.3 NHCO.sub.2 PNB,                                             Example 17.                                         ##STR129##  H  CH.sub.2 OH                                                                          CH.sub.3                                                                             From Compound 1. of Example  30 in                                             reaction with methyl  formimidate                                              hydrochloride  in water at pH 8.5.                  ##STR130##  H  CH.sub.2 OH                                                                          CH.sub.3                                                                             From Compound 1 of Example  30 in                                              reaction with ethyl   acetimidate                                              hydrochloride  in water at pH 8.5.                  ##STR131##  H  CH.sub.2 OH                                                                          CH.sub.3                                                                              ##STR132##                                         ##STR133##  H  CH.sub.2 OH                                                                          CH.sub.3                                                                             As in 2., above.                                    ##STR134##  H  CH.sub.2 OH                                                                          CH.sub.3                                                                             As in 3., above.                                    ##STR135##  H  CH.sub.2 OH                                                                          CH.sub.3                                                                              ##STR136##                                         ##STR137##  H  CH.sub.2 OH                                                                          CH.sub.3                                                                             As in 2., above.                                    ##STR138##  H  CH.sub.2 OH                                                                          CH.sub.3                                                                             As in 3., above.                               10.                                                                                 ##STR139##  H  CH.sub.2 OH                                                                          CH.sub.3                                                                              ##STR140##                                         ##STR141##  H  CH.sub.2 OH                                                                          CH.sub.3                                                                             From HSCH(CH.sub.3)CH.sub.2 NHCO.sub.2                                         PNB, Example 17.                               12. CH.sub.3     H  CH.sub.2 OH                                                                          CH.sub.3                                                                             From HSCH.sub.3, Example 17.                        ##STR142##  H  CH.sub.2 OH                                                                          CH.sub.3                                                                             From HSφ, Example 17.                           ##STR143##  H  CH.sub.2 OH                                                                          CH.sub.3                                                                              ##STR144##                                         ##STR145##  H  CH.sub.2 OH                                                                          CH.sub.3                                                                             From HSCH.sub.2 CH(CH.sub.3)NHCO.sub.2                                         PNB, Example 17.                                    ##STR146##  H  CH.sub.2 OH                                                                          CH.sub.3                                                                             From HSCH.sub.2 CH(CH.sub.3)NHCO.sub.2                                         PNB Example 17.                                     ##STR147##  H  CH.sub.2 OH                                                                          CH.sub.3                                                                              ##STR148##                                    18. SCH.sub.2 CH.sub.2 NH.sub.2                                                                 H  CH.sub.2 OH                                                                          CH.sub.3                                                                             Example 17.                                    19. SCH.sub.2 CH.sub.2 NH.sub.2                                                                 H                                                                                  ##STR149##                                                                          CH.sub.3                                                                             From azetidinone of Example 24, followed                                       the procedure of Example 17.                   20. SCH.sub.2 CH.sub.2 NH.sub.2                                                                 H                                                                                  ##STR150##                                                                          CH.sub.3                                                                             From azetidinone of Example 22, followed                                       the procedure of Example 23 except                                             substituting LiCL for LiN.sub.3 and                                            Example 17.                                    21. SCH.sub.2 CH.sub.2 NH.sub.2                                                                 CH.sub.3                                                                           ##STR151##                                                                          CH.sub.3                                                                             From azetidinone of Example 6 followed                                         the procedure of Example 7 except                                              substituting acetaldehyde for                                                  formaldehyde and Example 17.                   22. Sφ       CH.sub.3                                                                           ##STR152##                                                                          CH.sub.3                                                                             From azetidinone of Example 6, followed                                        Example 17 except substituting thio-                                           phenol for cysteamine.                         23. SCH.sub.2 CH.sub.2 CH.sub.2 NH.sub.2                                                        CH.sub.3                                                                           ##STR153##                                                                          CH.sub.3                                                                             Same as compound 21 except using                                               aminopropanethiol instead of aminoethane-                                      hiol                                           24. Sφ       CH.sub.3                                                                           ##STR154##                                                                          CH.sub.3                                                                             Same as compound 21, except using                                              thiophenol instead of aminoethanethiol.        25. SCH.sub.2 CH.sub.2 NH.sub.2                                                                 H  CH.sub.2 OH                                                                          C.sub.2 H.sub.5                                                                      Same as for (18). except                                                       replacing 1-acetoxyl-2-methyl-                                                 1,3-butadiene with 1-acetoxyl-                                                 2-ethyl-1,3-butadiene in                                                       Example 2, Step A.                             26. SCH.sub.2 CH.sub.2 NH.sub.2                                                                 CH.sub.3                                                                           ##STR155##                                                                           ##STR156##                                                                          Same as for (21), except replacing                                             1-acetoxyl- 2-methyl-butadiene with                                            1-acetoxyl-2-isopropyl- butadiene.             __________________________________________________________________________

EXAMPLE 31 Preparation of Pharmaceutical Compositions

One such unit dosage form is prepared by mixing 120 mg of 1-methyl-6-(1-hydroxymethyl)-2-(2-aminoethylthio)-1-carbadethiapen-2-em-3-carboxylic acid with 20 mg of lactose and 5 mg of magnesium stearate and placing the 145 mg. mixture into a No. 3 gelatin capsule. Similarly, by employing more of the active ingredient and less lactose, other dosage forms can be put up in No. 3 gelatin capsules and should it be ncessary to mix more than 145 mg. of ingredients together larger capsules such as compressed tablets and pills can also be prepared. The following examples are illustrative of the preparation of pharmaceutical formulations:

    ______________________________________                                         TABLET                 PER TABLET                                              ______________________________________                                         1-methyl-6-(1-hydroxymethyl)-2-                                                (2-aminoethylthio)-1-carbadethiapen-                                           2-em-3-carboxylic acid 125 mg.                                                 Dicalcium Phosphate    192 mg.                                                 Cornstarch, U.S.P.      6 mg.                                                  Lactose, U.S.P.        190 mg.                                                 Magnesium Stearate     Balance                                                 ______________________________________                                    

The active ingredient is blended with the dicalcium phosphte, lactose and about half of the cornstarch. The mixture is then granulated with 15% cornstarch paste (6 mg) and rough-screened. It is dried at 45° C. and screened again through No. 16 screens. The balance of the cornstarch and the magnesium stearate is added and the mixture is compressed into tablets, approximately 0.5 inch in diameter each weighing 800 mg.

    ______________________________________                                         PARENTAL SOLUTION                                                              Ampoule:                                                                       ______________________________________                                         1-methyl-6-(1-hydroxymethyl)-2-(2-                                             aminoethylthio)-1-carbadethiapen-2-em-3-                                       carboxylic acid               500 mg.                                          Diluent: Sterile Water for Injection                                                                         5 cc                                             OPTHALMIC SOLUTION                                                             1-methyl-6-(1-hydroxymethyl)-2-                                                (2-aminoethylthio)-1-carbadethia-                                              pen-2-em-3-carboxylic acid    100 mg                                           Hydroxypropylmethyl cellulose 5 mg.                                            Sterile water          to     1 ml.                                            OTIC SOLUTION                                                                  1-methyl-6-(1-hydroxymethyl)-2-                                                (2-aminoethylthio)-1-carbadethia-                                              pen-2-em-3-carboxylic acid    100 mg.                                          Benzalkonium chloride         0.1 mg.                                          Sterile water          to     1 ml.                                            TOPICAL OINTMENT                                                               1-methyl-6-(1-hydroxymethyl)-2-                                                (2-aminoethylthio)-1-carbadethia-                                              pen-2-em-3-carboxylic acid    100 mg.                                          Polyethylene Glycol 4000 U.S.P.                                                                              400 mg.                                          Polyethylene Glycol 400 U.S.P.                                                                               1.0 gram.                                        ______________________________________                                    

The active ingredient in the above formulations may be administered alone or in combination with other biologically active ingredients as, for example, with other antibacterial agents such as lincomycin, a penicillin, streptomycin, novobiocin, gentamicin, neomycin, colistin and kanamycin, or with other therapeutic agents such as probenecid. 

What is claimed is:
 1. A compound having the structure: ##STR157## wherein R is H; or a pharmaceutically acceptable salt cation; and R¹, R⁶, R⁷ and R⁸ are independently selected from the group consisting of hydrogen, (R¹ is not H) substituted and unsubstituted: alkyl, alkenyl, alkynyl, having from 1-10 carbon atoms; cycloalkyl, cycloalkylalkyl, and alkylcycloalkyl, having 3-6 carbon atoms in the cycloalkyl ring and 1-6 carbon atoms in the alkyl moieties; phenyl; aralkyl, aralkenyl, and aralkynyl wherein the aryl moiety is phenyl and the alkyl chain has 1-6 carbon atoms; wherein the substituent or substituents relative to the above-named radicals are selected from the group consisting of: amino, mono-, di- and trialkylamino, hydroxyl, alkoxyl, mercapto, alkylthio, phenylthio, sulfamoyl, amidino, guanidino, nitro, chloro, bromo, fluoro, cyano and carboxy; and wherein the alkyl moieties of the above-recited substituents have 1-6 carbon atoms; when R⁸ is 2-aminoethyl, and when R⁷ /R⁶ is hydrogen, then R⁶ /R⁷ is not 1-hydroxyethyl.
 2. A compound according to claim 1 wherein R¹ is alkyl, phenyl, benzyl, or cycloalkyl.
 3. A compound according to claim 1 wherein R⁶ is H or methyl and R⁷ is alkyl, phenyl, aralkyl or hydroxyl-substituted alkyl, phenyl or aralkyl.
 4. A compound according to claim 1 wherein: R⁶ is hydrogen or methyl and R⁸ is selected from the group consisting of:H, CH₃, (CH₂)₂ NH₂, C(CH₃)₂ CH₂ NH₂, ##STR158## CH₂ CH₂ CH₂ NH₂, CH₂ CH(CH₃)NH₂, ##STR159## and R⁷ is selected from: ##STR160##
 5. A compound according to claim 1 having the structure: ##STR161## and its pharmaceutically acceptable salts.
 6. An antibiotic pharmaceutical composition comprising a therapeutically effective amount of a compound according to claim 1 and a pharmaceutical carrier therefor. 